# RuntimeError: The session is unavailable because no secret key was set. Set the secret_key on the application to something unique and secret.

- **ID:** `python/flask-missing-secret-key`
- **Domain:** python
- **Category:** config_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

Flask requires a secret key to use sessions. If app.secret_key is not set, session operations fail.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.x | active | — | — |

## Workarounds

1. **Set secret_key on the Flask app instance** (95% success)
   ```
   app.secret_key = 'your-secret-key'
   ```
2. **Use os.urandom to generate a secure key** (95% success)
   ```
   import os
app.secret_key = os.urandom(24)
   ```

## Dead Ends

- **Setting secret_key to an empty string** — An empty string is not considered a valid secret key. (90% fail)
- **Using app.config['SECRET_KEY'] = 'mysecret' after first session access** — The secret key must be set before the first session usage. (70% fail)